In a photoresist process, which a type of semiconductor manufacturing process, a resist is applied to a surface of a semiconductor wafer (hereinafter, referred to as a “wafer”) that serves as a substrate, and the formed resist film is exposed in a predetermined pattern and then developed, thereby forming a resist pattern. The wafer is subjected to a heat treatment before and after the resist is applied and the resist film is developed.
In some cases, modules of a substrate processing apparatus perform the respective processes for the wafer while gas flow is generated on a surface of the wafer. For example, in a heating module for performing a heat treatment, the gas flow is generated on the surface of the wafer in order to prevent sublimates, which may be generated from various films such as the resist film formed on the wafer during the heat treatment, from being attached to the wafer. In addition, in a module for forming a resist film, a resist film is formed, by spin coating, and in order to prevent mists from being attached to the wafer, while the interior of a cup onto which a wafer is loaded is evacuated and simultaneously gas is supplied onto the wafer surface from an upper portion of the cup.
However, if the directions and speeds of the gas flow generated in respective portions of the planar surface of the wafer are in disorder, a deviation in a temperature distribution on the planar surface of the wafer also occurs, which may result in deterioration of process uniformity on the surface of the wafer. In addition, if a deviation in the gas flow occurs between modules which perform the same process for wafers, the process uniformity between the wafers may be deteriorated. In order to prevent such deterioration, the direction and speed of the gas flow is previously calculated through a simulation by a computer, and the gas flow of a module has been adjusted accordingly. However, the higher process uniformity on a planar surface of a wafer and between wafers is required. Under these circumstances, a jig (sensor wafer) having a shape generally similar to a wafer may be used to measure a distribution of the gas flow directions and speeds by means of sensors provided on the surface of the jig.
In order to reduce the effort required in the measurement, the sensor wafer may be transferred between the aforementioned modules in the same way as the wafer, and the data of the gas flow directions and speeds are automatically obtained in each module or a transfer path of the wafer. However, to this end, a variety of components, in addition to the sensors, need to be installed on the sensor wafer. Specifically, it is under consideration to provide a power supply unit for supplying the sensors with power, a memory for storing the data obtained from the sensors, a transmission unit for transmitting the data to the outside, and the like.
However, even though there is an objective to obtain the data of the gas flow directions and speeds when a wafer is processed, the shape of the sensor wafer cannot be much different from the shape of the wafer. That is, the positions in which the components can be disposed are limited. In addition, the sensors are disposed in the positions in which the components cause a little disorder to the gas flow. That is, the positions in which the sensor can be disposed are limited, and under such condition, there is a need for a technique to measure the gas flow with high accuracy. In the prior art, a problem of such a sensor layout is not considered, and the sensors can detect only the gas flow speeds in a predetermined straight direction. Thus, it is insufficient to measure a distribution of the gas flow directions and speeds with high accuracy.